pms: fix build error in pms_probe()

Mauro,

If possible, I'd prefer folding this patch into commit 8173090acb33 ("v4l: fix compiler warnings"), which introduced the build error. Thank you!

drivers/media/video/pms.c: In function ‘pms_probe’:
drivers/media/video/pms.c:1047:2: error: implicit declaration of function ‘kzalloc’ [-Werror=implicit-function-declaration] drivers/media/video/pms.c:1116:2: error: implicit declaration of function ‘kfree’ [-Werror=implicit-function-declaration]

---
 drivers/media/video/pms.c |    1 +
 1 file changed, 1 insertion(+)

index af2d908..77f9c92 100644
@@ -26,6 +26,7 @@
 #include <linux/fs.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
+#include <linux/slab.h>
 #include <linux/ioport.h>
 #include <linux/init.h>
 #include <linux/mutex.h>

1.7.10